Abstract

The human microbiota and probiotics are key players to modulate human health. Microbial cells, as a whole, have either been known to physically react with intestinal surfaces or to produce some enzymes and metabolites to impart a positive or negative impact on human health. Moreover, their specialized metabolites have a profound role in the generation of multivariate clinical responses in humans, with an influence on hosts’ metabolism and immunity. Gut microbiota and probiotics are known for their influence on hosts’ physiology.

We review clinical trials based on microbiota composition to correlate health status of humans with their gut microbiota, along with few examples of effects of microbial perturbation on health and disease. The chapter also explains the roles of metabolites of human microbiota, in addition to their impacts on hosts’ physiology. Besides the positive influences of microbes on humans, negative effects of the microbial metabolism, such as inactivating the pharmacological activity of drugs are also discussed, Selected examples for the roles of gut microbiota in human metabolism, using their enzymatic repertoire for degradation of otherwise indigestible dietary components, are reviewed. We present the mode of action of newly identified effector molecules, polysaccharides, outer membrane proteins, pili, muropeptides, and CpG-rich DNA, both for human microbiota and probiotics (Lactobacillus and Bifidobacterium strains). Besides effector molecules, clinical outcomes of probiotics (as whole live cells) are also discussed. Moreover, health-improving probiotic metabolites, including vitamins, bacteriocins, and bioactive peptides, are reviewed. In the end, a new perspective of developing a microbial global positioning system (mGPS) for segregation of human population on the basis of their microbiota is discussed.